That doesn't sound far off from a PTO generator, assuming you've got the right interconnects exposed seems reasonable. From my limited understanding most diesel electrics go Diesel -> AC -> DC -> AC -> Wheels. If your taking power from the first AC part the engine RPM determines frequency(as with a PTO generator). Most diesels used in these applications with similarly buffered powertrains(some tractors/heavy machinery with HSTs/etc) have good governors to keep the engine from running away.

From the article it sounded like it wasn't ideal(there was damage to the gearbox from driving the engines down the road).

(as an aside this is why I think a diesel-electric tractor or pure electric would be pretty nifty thing)